End seal for an absorbent article

ABSTRACT

The present invention relates to absorbent articles, such as diapers and sanitary napkins, and cores useful for such articles. More specifically, the invention relates to an absorbent article having a longitudinal centerline and a transverse centerline, the absorbent article comprising an absorbent core, the core comprising a storage layer and a wearer facing side oriented towards a wearer when the article is being worn and an opposed garment facing side, the absorbent article further comprising a liquid pervious topsheet on the wearer facing side of the core and a liquid pervious backsheet on the garment facing side of the core, the core further comprising a first core wrap sheet covering the wearer facing side of the storage layer and a second core wrap sheet covering the garment facing side of the storage layer the first core wrap sheet being joined to the second core wrap sheet along at least one transverse stripe of juncture, wherein the stripe of juncture covers a total area and the stripe of juncture provides a bond strength of at least 1 N/cm between the first core wrap sheet and a second core wrap sheet as measured as tensile strength in the longitudinal direction and wherein the stripe of juncture comprises an open area of at least 20% of the total area.

FIELD OF THE INVENTION

The present invention relates to absorbent articles, such as diapers andsanitary napkins, and cores useful for such articles. More specifically,the present invention relates to absorbent cores for such articles andthe enveloping of such cores.

BACKGROUND OF THE INVENTION

Disposable absorbent articles are broadly available and consumers areused to a high performance for the collecting and retaining of menses(in the case of sanitary napkins or panty liners) or for the collectingand retaining urine and fecal material (in the case of e.g. disposablediapers). From such articles consumers expect a superior absorbencybehaviour and at the same time expect excellent the wearing comfort andthe dryness when being worn.

Often, such articles comprise multiple absorbent members, at least onemember being primarily designed to store liquid, and at least one othermember primarily designed to acquire and/or distribute liquid, themembers typically being encapsulated between a topsheet (on the wearerfacing side) and a backsheet (on the garment facing side).

In modern absorbent articles the absorbent core will typically comprisea super-absorbent material in combination with a fibrous material, forexample cellulose. In particular, the storage layer will be providedfrom a combination of such materials. It is important to maintain theintegrity of such absorbent core, both when the article is dry and whenthe article is wet, that means before use and in use. It is alsoimportant to prevent the escape of any of the absorbent materialsproviding the core, in particular the escape of super-absorbentmaterials, which are often provided in the form of particles. The escapeof super-absorbent materials from the core could ultimatively lead tocontact of such super-absorbent materials with the skin of the wearer.This phenomenon is known as gel on skin (as the super-absorbentmaterials are often also referred to as hydrogels). However, such gel onskin occurrences are considered undesirable as many consumers considerthe skin contact of such super-absorbent material to be unpleasant. Somerecent absorbent articles, especially disposable diapers, employrelatively open topsheet structures. These open topsheets promote theabsorbance or at least the adherence of high viscosity exudates, such asbowel movement. However, when it's specifically comes to gel on skinproblems, these open topsheet structures present a challenge, as they donot represent a highly effected barrier for super-absorbent particles,which may escape from the absorbent core of the absorbent article.

U.S. Pat. No. 4,573,986 (filed in 1984) discloses an early attempt forobviating lifting out of fibers and particulate matters from theabsorbent core of an absorbent garment. A wet-strength-tissue envelopeis disclosed in which the absorbent core is disposed and secured. Thewet-strength-tissue paper or a similar laminate is secured in face toface relation with the core by an open pattern of adhesive, which may,for example, comprise a fine pattern of globulettes of adhesive.Alternatively, a reticulated network of filaments of adhesives can beused.

EP 847 263 (filed in 1995) discloses a more recent core wrap material:Disclosed is a core wrap made from a fibrous non-woven web, preferably apolypropylene melt-blown non-woven material. This core wrap material maybe folded over on itself and then sealed using, for example, adhesives,heat and/or pressure. In this context, ultrasonic bonder,thermo-mechanically bonding means and adhesives are specificallydisclosed as suitable sealing means.

EP 1 088 537 (filed in 2000) discloses a highly water absorbent sheet.This absorbent sheet comprises fine cellulose fibers which provide afibrous network holding solid super-absorbent particles in position. Inorder to prevent the escaping of such super-absorbent particles, thedisclosed absorbent sheet relies on a hot-melt adhesive forming afurther fibrous network and covering the super-absorbent particles.

WO 00/64396 (filed in 2000) discloses yet a further approach forintegrity and immobilization enhancement for an absorbent member. Themethod comprises the application of a foamable movement obstructionagent to an absorbent member.

As to provide the desired absorbency to the article, at least thestorage member will typically comprise super-absorbent material, whichis admixed with the traditionally used pulp fiber material. Suchsuper-absorbent materials can absorb many times (e.g. 10, 20 or 30times) their own weight and are therefore very helpful when designing anarticle of improved fluid handling properties. Many recent productsemploy higher and higher concentrations of super-absorbent materials,that is concentrations in excess of 50% of the total weight of thestorage member. These products achieve a high absorbing capacity with avery thin storage member and are thereby typically overall thinproducts. While super-absorbent materials can store very large amountsof liquid, they are often not able to distribute the liquid from thepoint of impact to more remote areas of the absorbent article and toacquire the liquid as fast as it may be received by the article.

Hence, the prior art has disclosed various attempts to prevent theescaping of super-absorbent particles from the absorbent core. However,especially when it comes to absorbent cores with high concentrations ofsuper-absorbent material and the use of relatively open topsheetstructures, an even more efficient prevention of the escaping ofsuper-absorbent particles from the absorbent core is desirable.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, an absorbentarticle is provided that extends along a longitudinal axis and atransverse axis. The absorbent article includes a topsheet, a backsheet,and an absorbent core disposed between the topsheet and the backsheet.The defines a wearer facing side oriented towards a wearer when thearticle is being worn and an opposed garment facing side. The coreincludes 1) a storage layer having a wearer facing side and an opposedgarment facing side, 2) a first core wrap sheet covering the wearerfacing side of the storage layer, and 3) a second core wrap sheetcovering the garment facing side of the storage layer. The first corewrap sheet is joined to the second core wrap sheet along at least onetransverse stripe of juncture. The stripe of juncture covers a totalarea. The stripe of juncture provides a bond strength of at least 1 N/cmbetween the first core wrap sheet and a second core wrap sheet asmeasured as tensile strength in the longitudinal direction. The stripeof juncture comprises an open area of at least 20% of the total area.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims pointing out anddistinctly claiming the present invention, it is believed the same willbe better understood by the following drawings taken in conjunction withthe accompanying specification wherein like components are correspond tolike reference numbers throughout, and in which:

FIG. 1 is a top plan view of a disposable diaper, with the upper layerspartially cut away;

FIG. 2 is a cross-sectional view of the disposable diaper shown in FIG.1; and

FIG. 3 is a top plan view of the storage layer comprised by theabsorbent core of a disposable diaper as shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, the following terms have the following meanings:

“Absorbent article” refers to devices that absorb and contain liquid,and more specifically, refers to devices that are placed against or inproximity to the body of the wearer to absorb and contain the variousexudates discharged from the body. Absorbent articles include but arenot limited to diapers, adult incontinent briefs, training pants, diaperholders and liners, sanitary napkins and the like. Absorbent articlesalso include wipes, such as household cleaning wipes, baby wipes, andthe like.

“Disposable” is used herein to describe articles that are generally notintended to be laundered or otherwise restored or reused i.e., they areintended to be discarded after a single use and, preferably, to berecycled, composted or otherwise disposed of in an environmentallycompatible manner.

“Disposed” is used to mean that an element(s) is formed (joined andpositioned) in a particular place or position as a unitary structurewith other elements or as a separate element joined to another element.

“Diaper” refers to an absorbent article generally worn by infants andincontinent persons about the lower torso.

The terms “thickness” and “caliper” are used herein interchangeably.

“Attached” or “Joined” encompasses configurations whereby an element isdirectly secured to another element by affixing the element directly tothe other element, and configurations whereby an element is indirectlysecured to another element by affixing the element to intermediatemember(s) which in turn are affixed to the other element.

“Comprise,” “comprising,” and “comprises” is an open ended term thatspecifies the presence of what follows e.g. a component but does notpreclude the presents of other features, elements, steps or componentsknown in the art, or disclosed herein.

The term “hydrophilic” describes fibers or surfaces of fibers, which arewettable by aqueous fluids (e.g. aqueous body fluids) deposited on thesefibers. Hydrophilicity and wettability are typically defined in terms ofcontact angle and the strike through time of the fluids, for examplethrough a nonwoven fabric. This is discussed in detail in the AmericanChemical Society publication entitled “Contact angle, wettability andadhesion”, edited by Robert F. Gould (Copyright 1964). A fiber orsurface of a fiber is said to be wetted by a fluid (i.e. hydrophilic)when either the contact angle between the fluid and the fiber, or itssurface, is less than 90°, or when the fluid tends to spreadspontaneously across the surface of the fiber, both conditions arenormally co-existing. Conversely, a fiber or surface of the fiber isconsidered to be hydrophobic if the contact angle is greater than 90°and the fluid does not spread spontaneously across the surface of thefiber.

The terms “fiber” and “filament” are used interchangeably.

The terms “nonwoven”, “nonwoven fabric” and “nonwoven web” are usedinterchangeable.

The disposable article 20 has two centerlines, a longitudinal centerline100 and a transverse centerline 110.

The term “longitudinal”, as used herein, refers to a line, axis ordirection in the plane of the disposable article 20 that is generallyaligned with (e.g., approximately parallel to) a vertical plane whichbisects a standing wearer into left and right body halves when thedisposable article 20 is worn.

The terms “transverse” or “lateral” as used herein, are interchangeable,and refer to a line, axis or direction which lies in the plane of thedisposable article 20 that is generally perpendicular to thelongitudinal direction.

Absorbent Articles

FIG. 1 is a plan view of a diaper 20, illustrated in accordance with oneembodiment of an absorbent article according to the present invention,is shown in its flat out, uncontracted state (i.e., without elasticinduced contraction). Portions of the structure are cut away to moreclearly show the underlying structure of the diaper 20. The portion ofthe diaper 20 that contacts a wearer is facing the viewer. The chassis22 of the diaper 20 in FIG. 1 comprises the main body of the diaper 20.The chassis 22 comprises an outer covering including a liquid pervioustopsheet 24 and/or a liquid impervious backsheet 26. The chassis mayalso include most or all of the absorbent core 28 encased between thetopsheet 24 and the backsheet 26. The chassis preferably furtherincludes side panels 30, leg cuffs 32 and a waist feature 34. The legcuffs and the waist feature typically comprise elastic members 33. Oneend portion of the diaper 20 is configured as the front waist region 36of the diaper 20. The opposite end portion is configured as the rearwaist region 38 of the diaper 20. An intermediate portion of the diaper20 is configured as the crotch region 37, which extends longitudinallybetween the front and rear waist regions 36 and 38. The crotch region 37is that portion of the diaper 20 which, when the diaper 20 is worn, isgenerally positioned between the wearer's legs. The waist regions 36 and38 may include a fastening system comprising fastening members 40preferably attached to the rear waist region 38 and a landing zone 42attached to the front waist region 36. The diaper 20 has a longitudinalaxis and centerline 100 and a transverse axis and centerline 110. Theperiphery of the diaper 20 is defined by the outer edges of the diaper20 in which the longitudinal edges 44 run generally parallel to thelongitudinal axis 100 of the diaper 20 and the end edges 46 rungenerally parallel to the transverse axis 110 of the diaper 20.

For unitary absorbent articles, the chassis 22 comprises the mainstructure of the diaper with other features added to form the compositediaper structure. While the topsheet 24, the backsheet 26, and theabsorbent core 28 may be assembled in a variety of well-knownconfigurations, preferred diaper configurations are described generallyin U.S. Pat. No. 5,569,234 entitled “Disposable Pull-On Pant” issued toBuell et al. on Oct. 29, 1996; and U.S. Pat. No. 6,004,306 entitled“Absorbent Article With Multi-Directional Extensible Side Panels” issuedto Robles et al. on Dec. 21, 1999.

The topsheet 24 in FIG. 1 may be fully or partially elasticized or maybe foreshortened to provide a void space between the topsheet 24 and theabsorbent core 28. Exemplary structures including elasticized orforeshortened topsheets are described in more detail in U.S. Pat. No.5,037,416 entitled “Disposable Absorbent Article Having ElasticallyExtensible Topsheet” issued to Allen et al. on Aug. 6, 1991; and U.S.Pat. No. 5,269,775 entitled “Trisection Topsheets for DisposableAbsorbent Articles and Disposable Absorbent Articles Having SuchTrisection Topsheets” issued to Freeland et al. on Dec. 14, 1993.

The backsheet 26 in FIG. 1 is generally the portion of the diaper 20positioned with the absorbent core 28 between the backsheet 26 and thetopsheet 24. The backsheet 26 may be joined with the topsheet 24. Thebacksheet 26 prevents the exudates absorbed by the absorbent core 28 andcontained within the article 20 from soiling other external articlesthat may contact the diaper 20, such as bed sheets and undergarments. Inpreferred embodiments, the backsheet 26 is substantially impervious toliquids (e.g., urine) and comprises a laminate of a nonwoven and a thinplastic film such as a thermoplastic film having a thickness of about0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils). Suitable backsheetfilms include those manufactured by Tredegar Industries Inc. of TerreHaute, Ind. and sold under the trade names X15306, X10962, and X10964.Other suitable backsheet materials may include breathable materials thatpermit vapors to escape from the diaper 20 while still preventingexudates from passing through the backsheet 26. Exemplary breathablematerials may include materials such as woven webs, nonwoven webs,composite materials such as film-coated nonwoven webs, and microporousfilms such as manufactured by Mitsui Toatsu Co., of Japan under thedesignation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex.,under the designation EXXAIRE.

The absorbent core 28 in FIG. 1 generally is disposed between thetopsheet 24 and the backsheet 26. The absorbent core 28 may comprise anyabsorbent material that is generally compressible, conformable,non-irritating to the wearer's skin, and capable of absorbing andretaining liquids such as urine and other certain body exudates. Theabsorbent core 28 may comprise a wide variety of liquid-absorbentmaterials commonly used in disposable diapers and other absorbentarticles such as comminuted wood pulp, which is generally referred to asair felt. Examples of other suitable absorbent materials include crepedcellulose wadding; melt blown polymers, including co-form; chemicallystiffened, modified or cross-linked cellulosic fibers; tissue, includingtissue wraps and tissue laminates, absorbent foams, absorbent sponges,superabsorbent polymers, absorbent gelling materials, or any other knownabsorbent material or combinations of materials. The absorbent core mayfurther comprise minor amounts (typically less than 10%) of non-liquidabsorbent materials, such as adhesives, waxes, oils and the like.

Exemplary absorbent structures for use as the absorbent assemblies aredescribed in U.S. Pat. No. 4,834,735, entitled “High Density AbsorbentMembers Having Lower Density and Lower Basis Weight Acquisition Zones”,issued to Alemany et al. on May 30, 1989; and U.S. Pat. No. 5,625,222entitled “Absorbent Foam Materials For Aqueous Fluids Made From highInternal Phase Emulsions Having Very High Water-To-Oil Ratios” issued toDesMarais et al. on Jul. 22, 1997.

The diaper 20 may also include such other features as are known in theart including front and rear ear panels, waist cap features, elasticsand the like to provide better fit, containment and aestheticcharacteristics. Such additional features are well known in the art andare described in U.S. Pat. No. 3,860,003 entitled “Contractable sideportions for disposable diaper” issued to Buell et al. on Jan. 14, 1975and U.S. Pat. No. 5,151,092 entitled “Absorbent article with dynamicelastic waist feature having a predisposed resilient flexural hinge”issued to Buell et al. on Sep. 29, 1992.

In order to keep the diaper 20 in place about the wearer, the waistregions 36 and 38 may include a fastening system comprising fasteningmembers 40 preferably attached to the rear waist region 38. In apreferred embodiment the fastening system further comprises a landingzone 42 attached to the front waist region 36. The fastening member isattached to the front waist region 36, preferably to the landing zone 42to form leg openings and an article waist.

Diapers 20 constructed in accordance with certain aspects of the presentinvention may be provided with a re-closable fastening system or mayalternatively be provided in the form of pant-type diapers.

The fastening system and any component thereof may include any materialsuitable for such a use, including but not limited to plastics, films,foams, nonwoven webs, woven webs, paper, laminates, fiber reinforcedplastics and the like, or combinations thereof. It may be preferablethat the materials making up the fastening device be flexible. Theflexibility is designed to allow the fastening system to conform to theshape of the body and thus, reduces the likelihood that the fasteningsystem will irritate or injure the wearer's skin.

FIG. 2 shows a cross-sectional view of FIG. 1 taken in the transverseaxis 110. Starting from the wearer facing side the diaper comprises thetopsheet 24, the components of the absorbent core 28, and the backsheet26. The absorbent core preferably comprises an acquisition system 50,which comprises an upper acquisition layer 52 facing towards the wearerand a lower acquisition layer 54. In one preferred embodiment the upperacquisition layer comprises a nonwoven fabric whereas the loweracquisition layer preferably comprises a mixture of chemicallystiffened, twisted and curled fibers, high surface area fibers andthermoplastic binding fibers. In another preferred embodiment bothacquisition layers are provided from a non-woven material, which ispreferably hydrophilic. The acquisition layer preferably is in directcontact with the storage layer 60.

The storage layer 60 is preferably wrapped by a core wrap material. Inone preferred embodiment the core wrap material comprises a first corewrap layer 56 (top layer) and a second core wrap layer 58 (bottomlayer). The first core wrap layer 56 and the second core wrap layer 58can be provided from a non-woven material. One preferred material is aso-called SMS material, comprising a spunbonded, a melt-blown and afurther spunbonded layer. The first core wrap layer 56 and the secondcore wrap layer 58 may be provided from two or more separate sheets ofmaterials or they may be alternatively provided from a unitary sheet ofmaterial. Such a unitary sheet of material may be wrapped around thestorage layer 60, e.g. in a C-fold. The first core wrap layer 56 and thesecond core wrap layer 58 may also be joined to each other, preferablyalong their periphery. In one preferred option both layers are joinedalong their longitudinal peripheries, in other embodiments they arejoined along the transversal peripheries, or along the longitudinal andthe transversal peripheries. The joining can be achieved my multiplemeans well known in the art, eg. by adhesive means, using a continuousor a discontinuous pattern, and preferably a linear or curvilinearpattern.

The storage layer 60 typically comprises fibrous materials, mixed withsuper-absorbent, absorbent gelling materials. Other materials describedabove as suitable for the absorbent core 28 may also be comprised.Exemplary storage layers can comprise a superabsorbent material in anamount corresponding to at least 30%, or at least 40%, or at least 50%,or at least 60%, or at least 70%, or at least 80% or at least 90% of thetotal weight of the storage layer.

A upper liquid acquisition layer 52 useful in a diaper can comprise anyof the non-woven fabrics described below. A preferred liquid acquisitionlayer 52 comprises a binder comprising a styrene-butadiene latex binder.Preferably, the styrene-butadiene latex binder has a carboxylation levelof at least 10%, preferably at least 12%. Preferably, the upper liquidacquisition layer 52 comprises polyester fibers and the liquidacquisition layer comprises 20 to 40 weight percent of styrene-butadienelatex binder, and 60 to 80 weight percent of said polyester fibers. Evenmore preferably, the polyester fibers comprise 20 to 80 weight percentof a first type of fibers, and 20 to 80 weight percent of a second typeof fibers, the second type of fibers comprising spiral-crimp fibers.Highly preferred are upper liquid acquisition layers wherein the firsttype of fibers exhibits a flat crimp and wherein the second type offibers comprises hollow chemically homogeneous bi-component fibers. Alsohighly preferred are any upper liquid acquisition layers wherein thepolyester fibers are carded to form a nonwoven.

Preferred acquisition systems may also comprise superabsorbentmaterials. Such acquisition systems may also comprise a singleacquisition layer or multiple acquisition layers. Where multipleacquisition layers are comprised any of these layer may comprisesuperabsorbent materials. Such superabsorbent material may be comprisedin an amount corresponding to at least 30%, or at least 50% or at least70%, at times even in an amount of 100% of the total weight of therespective acquisition layer.

Nonwoven Fabrics

A nonwoven fabric is a manufactured sheet, web or batt of directionallyor randomly orientated fibers, bonded by friction, and/or cohesionand/or adhesion, excluding paper and products which are woven, knitted,tufted, stitch-bonded incorporating binding yarns or filaments, orfelted by wet-milling, whether or not additionally needled.

The fibres may be of natural or man-made origin. They may be staple orcontinuous filaments or be formed in situ.

Nonwoven fabrics can be formed by many processes such as meltblowing,spunbonding, carding. The basis weight of nonwoven fabrics is usuallyexpressed in grams per square meter (gsm).

Commercially available fibers have diameters ranging from less thanabout 0.001 mm to more than about 0.2 mm and they come in severaldifferent forms: short fibers (known as staple, or chopped), continuoussingle fibers (filaments or monofilaments), untwisted bundles ofcontinuous filaments (tow), and twisted bundles of continuous filaments(yarn). Fibers are classified according to their origin, chemicalstructure, or both. They can be braided into ropes and cordage, madeinto felts (also called nonwovens or nonwoven fabrics), woven or knittedinto textile fabrics, or, in the case of high-strength fibers, used asreinforcements in composites—that is, products made of two or moredifferent materials.

The nonwoven fabrics may comprise fibers made by nature (naturalfibers), made by man (synthetic or man-made), or combinations thereof.Example natural fibers include but are not limited to: animal fiberssuch as wool, silk, fur, and hair; vegetable fibers such as cellulose,cotton, flax, linen, and hemp; and certain naturally occurring mineralfibers. Synthetic fibers can be derived from natural fibers or not.Example synthetic fibers, which are derived from natural fibers, includebut are not limited to rayon and lyocell, both of which are derived fromcellulose, a natural polysaccharide fiber. Synthetic fibers, which arenot derived from natural fibers, can be derived from other naturalsources or from mineral sources. Example synthetic fibers not derivedfrom natural sources include but are not limited to polysaccharides suchas starch. Example fibers from mineral sources include but are notlimited to polyolefin fibers such as polypropylene, polyethylene fibersand polyester, which are derived from petroleum, and silicate fiberssuch as glass and asbestos.

Nonwoven webs can be formed by direct extrusion processes during whichthe fibers and webs are formed at about the same point in time, or bypreformed fibers, which can be laid into webs at a distinctly subsequentpoint in time. Example direct extrusion processes include but are notlimited to: spunbonding, meltblowing, solvent spinning, electrospinning,and combinations thereof typically forming layers.

Example “laying” processes include wetlaying and drylaying. Exampledrylaying processes include but are not limited to airlaying, carding,and combinations thereof typically forming layers. Combinations of theabove processes yield nonwovens commonly called hybrids or composites.Example combinations include but are not limited tospunbond-meltblown-spunbond (SMS), spunbond-carded (SC),spunbond-airlaid (SA), meltblown-airlaid (MA), and combinations thereof,typically in layers. Combinations which include direct extrusion can becombined at about the same point in time as the direct extrusion process(e.g., spinform and coform for SA and MA), or at a subsequent point intime. In the above examples, one or more individual layers can becreated by each process. For instance, SMS can mean a three layer, ‘sms’web, a five layer ‘ssmms’ web, or any reasonable variation thereofwherein the lower case letters designate individual layers and the uppercase letters designate the compilation of similar, adjacent layers.

The fibers in a nonwoven web are typically joined to one or moreadjacent fibers at some of the overlapping junctions. This includesjoining fibers within each layer and joining fibers between layers whenthere is more than one layer. Fibers can be joined by mechanicalentanglement, by chemical bond or by combinations thereof. Fibers canalso be joined by heat-bonding, which comprises techniques such asthrough-air bonding and thermobonding by use of heated calendar rolls.

Preferred Topsheets

Exemplary topsheets can be compliant, soft feeling, and non-irritatingto the wearer's skin. Further, the topsheet 24 should be liquidpervious, permitting liquids (e.g., urine) to readily penetrate throughits thickness. A suitable topsheet 24 may be manufactured from a widerange of materials, such as porous foams; reticulated foams; aperturedplastic films; or woven or nonwoven webs of natural fibers (e.g., woodor cotton fibers), synthetic fibers (e.g., polyester or polypropylenefibers), or a combination of natural and synthetic fibers. Preferably,the topsheet 24 is made of a hydrophobic material to isolate thewearer's skin from liquids contained in the absorbent core 28.Alternatively, the topsheet 24 may be surfactant treated to make ithydrophilic.

The topsheet 24 preferably has a plurality of apertures with aneffective aperture size of at least 0.2 square millimeters, morepreferably, the plurality of apertures have an effective aperture sizeof at least 0.5 square millimeters, even more preferably, the pluralityof apertures have an effective aperture size of at least 1.0 squaremillimeters, and most preferably, the plurality of apertures have aneffective aperture size of at least 2.0 square millimeters. Effectiveapertures are those which have a gray level of 18 or less on a standardgray level scale of 0-255, under the image acquisition parametersdescribed in EP 1 032 336 B1. An aperture having a material free area ofx square millimeters is to be understood as having an effective aperturesize of at least x square millimeters.

The topsheet 24 preferably has an effective open area of at least 15percent, more preferably the topsheet has an effective open area of atleast 20 percent, even more preferably, the topsheet has an effectiveopen area of at least 25 percent, and most preferably the topsheet hasan effective open area of at least 30 percent. Preferably, at least 50%or at least 75% of the topsheet surface are provided with suchapertures.

Preferred Absorbent Cores

All of the above described fibers and manufacturing techniques can beuseful for providing core wrap sheets in accordance with the principlesof the present invention.

Preferred core wrap sheets are made of a hydrophilic material to promoterapid transfer of liquids (e.g. urine) through at least the first corewrap sheet. If such core wrap sheets are made of a hydrophobic material,such material can be treated to be hydrophilic, for example by treatmentwith a surfactant.

There are multiple ways to envelope an absorbent core using a first corewrap sheet and a second core wrap sheet, all of which are within thescope of the present invention. For example, two separate wrap sheetsmay be used, the first core wrap sheet covering the wearer facing sideof the core and the second core wrap sheet covering the garment facingsided of the core. Both wrap sheets can then be joined alonglongitudinally extending stripes of juncture, one stripe of juncture toeach side of the absorbent core. Alternatively, the first core wrapsheet can be integral with the second core wrap sheet and be providedfrom one and the same sheet of material. Then, only one longitudinallyextending stripe of juncture needs to be employed as to achieve theenveloping. Such stripe of juncture can either be of the wearer facingside of the core, or on the garment facing side of the core on eitherlateral side of the core. The overlapping ends of the wrap sheetmaterial, which are to be joined by said stripe of juncture, can bearranged as to create a butt seal or can be arranged as to create anoverlapping seal. Both an overlapping seal and a butt seal can be joinedusing a stripe of juncture in accordance with certain aspects of thepresent invention.

The core wrap sheets (if present) can be not only joined by alongitudinally extending stripe of juncture (for example a side seal),but also by a transversally extending stripe of juncture, which istypically positioned either at the front end of the absorbent core or atthe rear end of the absorbent core or at both ends of the absorbentcore. Such a transversally extending stripe of juncture can be providedby the same means as a longitudinally extending stripe of juncture.

The stripe of juncture 72 may comprise different elements having abonding function, herein referred as bonding elements. For example,bonding elements can be provided by adhesive bonding, bythermo-mechanical bonding, by ultrasonic bonding and the like. The areaof a rectangle comprising all bonding elements of the stripe of juncture72 is herein referred to as the total area of the stripe of juncture 72.According to the present invention, however, the stripe of juncture alsocomprises an open area. Open area, as used herein, denotes an area whereno bonding elements are present.

In one preferred embodiment of the present invention, which is shown inFIG. 3, the bonding elements are threads of adhesives. These threads arepreferably created by slot coating, but can also be provided by sprayapplication. The plurality of threads is separated by a plurality ofareas comprising no adhesive. The threads preferably have a width of 0.5mm to 2 mm, most preferably of 1 mm and the areas comprising no adhesivepreferably have a width of 0.5 mm to 2 mm, most preferably of 1 mm. Whenboth areas have the same width, the stripe of juncture 72 has an openarea of 50% of the total area.

Generally, in accordance with the present invention, stripes of juncture72 having an open area of at least 20%, or at least 30%, or at least40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%,or at least 90% of their total area are preferred. However, the openarea should not be more than 95% of the total area as to ensure reliablebonding.

Preferably, as to achieve sufficient macroscopic bond strength thethreads of adhesive have a diameter of more than 100 micrometer, morepreferably of more than 250 or 500 micrometer.

Core wrap sheets according to the present invention are preferablyprovided in the form of non-woven webs. More preferably, they areprovided from polyolefin, more preferably from polypropylene. Preferredcore wrap sheets have a basis weight from 3 gram per m² to 50 gram perm², more preferably from 5 gram per m² to 30 gram per m², preferablyfrom 8 gram per m² to 15 gram m².

The stripe of juncture will provide certain bond strength between thecore wrap sheets. The stripe of junction will have its largest extensionin a first direction. The bond strength between the core wrap sheets, asused herein, is to be understood as the tensile strength in a seconddirection which is perpendicular to the first direction and within theplane defined by the core wrap sheets. To test tensile strength a testspecimen of 2.54 cm (1 inch) width is cut at a representative (typicallycentral) position by two cutting lines oriented in the second direction.Tensile strength is then measured using this test specimen of materialin accordance with ASTM method D 1876-01, which is modified as follows:The specimen length is 60 mm and unbonded ends of 10 mm length are usedfor clamping in the grips of the testing machine (see paragraph 5.2 of D1876-01). The portions of the first and second core wrap sheet formingpart of the specimen are used as flexible adherends (see paragraph 5.1of D 1876-01). Further, tensile strength is reported (in units of Newtondivided by centimeter specimen width; N/cm) as the maximum value of theobtained autographic curve (see paragraph 8.1 of D 1876-01).

According to the present invention the stripe of juncture 72 provides abond strength of at least 0.5 N/cm between the first core wrap sheet 56and a second core wrap sheet 58 as measured as tensile strength in thelongitudinal direction. Preferably the stripe of juncture 72 provides abond strength of at least 1.0 N/cm or 1.5 N/cm or 2 N/cm or 3 N/cm.

Without wishing to be bound by theory, it seems particularly beneficialto have stripes of juncture which comprise relatively large open areas.It appears that the occurrence of the gel-on-skin phenomenon is in partcaused by super-absorbent particles which in the process ofmanufacturing are captured within such a line of junction. When a stripeof juncture is provided by continuous adhesive application, thesuperabsorbent material is limited in its ability to swell by beingconfined by the adhesive providing the stripe of juncture. However, thesuper-absorbent particle is likely to swell once the article is in useand receives liquid. When this swelling is highly restricted by thepresence of adhesive, the swelling forces are typically high enough toallow swelling in the direction of the core wrap sheets. These core wrapsheets are typically provided by non-woven materials or tissue materialsor similar materials which are relatively week. Hence, wherever thestripe of juncture itself does not provide sufficient open area toaccommodate the swelling of super-absorbent particles, such particleswill expand in the direction of the core wrap sheets. Therefore, theyare likely to escape through the core wrap sheets, often also causingdamage to the core wrap sheets. This escaping of super-absorbentmaterial from the core and especially out of the areas of the stripes ofjuncture appears to noticeably contribute to occurrences of gel-on-skin.If, however, in accordance with the present invention a stripe ofjuncture comprising a sufficiently high open area is provided, thisadhesive application will lead to more room for swelling within thestripe of juncture. The adhesive will either find a sufficient open areawithin the stripe of juncture to allow for swelling without exerting anypressure against the wrap sheets and against surrounding adhesivematerial or surrounding adhesive material will be elastic enough as toallow for swelling within the stripes of juncture while no or verylittle pressure is exerted towards the core wrap sheets.

In view of these considerations it seems best to select the dimension ofthe bonding elements and of the areas free of bonding elements in viewof the size of the superabsorbent particles which could escape from theabsorbent core 28. The value to be considered specifically is the meandiameter of the super-absorbent particles.

The mean diameter is to be determined using EDANA method 420.2-02entitled “Particle size distribution”. This EDANA method is a sievingmethod and reports the mass fraction in percent for each particle sizefraction remaining on the different sieves employed. Based on thisreport the mean diameter is calculated according to ASTM test method D1921-96, namely paragraph 13 thereof entitled “Analysis of ParticleDistribution”.

The smallest dimension of the bonding elements should be at least 0.2times the mean diameter of the super-absorbent material (“MD”).Preferably the smallest dimension of the bonding elements is from 0.2 to3 times the MD, more preferably from 0.5 to 2 times the MD, mostpreferably from 0.8 to 1.2 times the MD. The bonding elements are thenlarge enough to create the macroscopically desirably bond strength andalso large enough to reliably capture and retain particles ofsuper-absorbent materials which in the production process are entrappedby the bonding elements. On the other hand, they do not unnecessarilyrestrict the available open area.

The smallest dimension of the open areas should be at least 0.5 timesthe MD, preferably is from 0.5 to 10 times the MD, more preferably from1 to 5 times the MD. The open areas are then large enough to allow forrelatively unrestricted swelling of the superabsorbent particles.

Hence, the stripes of juncture 72 according to the present inventionprovide a sufficient bond strength on a macro level (when looking at theperformance of the overall absorbent article), but at the same timesufficient weakness and swelling space on a micro level (when looking atthe environment of single particles of super-absorbent material).

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. An absorbent article extending along a longitudinal axis and atransverse axis, the absorbent article comprising: a topsheet; abacksheet; and an absorbent core disposed between the topsheet and thebacksheet, the core defining a wearer facing side oriented towards awearer when the article is being worn and an opposed garment facingside, wherein the core includes 1) a storage layer having a wearerfacing side and an opposed garment facing side, 2) a first core wrapsheet covering the wearer facing side of the storage layer, and 3) asecond core wrap sheet covering the garment facing side of the storagelayer, the first core wrap sheet being joined to the second core wrapsheet along at least one transverse stripe of juncture, the stripe ofjuncture covering a total area; wherein the stripe of juncture providesa bond strength of at least 1 N/cm between the first core wrap sheet anda second core wrap sheet as measured as tensile strength in thelongitudinal direction, and wherein the stripe of juncture comprises anopen area of at least 20% of the total area.
 2. The absorbent article asrecited in claim 1, wherein the stripe of juncture comprises an openarea from about 30% to about 95% of the total area.
 3. The absorbentarticle as recited in claim 1, wherein the bond strength is at least atleast 2 N/cm.
 4. The absorbent article as recited in claim 1, whereinthe stripe of juncture comprises a plurality of threads of adhesive thatare separated by a plurality of areas having no adhesive.
 5. Theabsorbent article as recited in claim 4, wherein the threads have adiameter of less than about 2 mm, preferably less than about 1.5 mm. 6.The absorbent article as recited in claim 4, wherein the threads have adiameter of more than about 100 micrometer.
 7. The absorbent articlerecited in claim 1 wherein the article comprises superabsorbentparticles having a mean diameter.
 8. The absorbent article as recited inclaim 7, wherein the threads have a width of at least 0.5 times the meandiameter.
 9. The absorbent article as recited in claim 7, wherein theareas having no adhesive have a width of at least 0.5 times the meandiameter.
 10. The absorbent article as recited in claim 1, wherein theline of juncture has a width measured in the longitudinal direction ofat least 20 mm.
 11. The absorbent article as recited in claim 1, whereinat least of the first core wrap sheet and the second core wrap sheet hasa basis weight from about 3 gram per m² to about 50 gram per m².
 12. Theabsorbent article as recited in claim 1, wherein the topsheet comprisesa plurality of pores having an effective aperture size of at least 2.0square millimeters.
 13. The absorbent article as recited in claim 1,wherein the topsheet is liquid pervious.
 14. The absorbent article asrecited in claim 1, wherein the backsheet is liquid impervious.